Thickness precision is one of the most important quality indexes for cold rolled strips. With the rise and development of industries like automobiles, aviation, household appliances, precision instruments, civil architecture, food cans, there are strict requirements on the thickness precision of cold rolled strips.
Tandem cold mill is one of the most complicated equipments with highest degree of automation and meeting the strictest requirements on precision in metallurgical industry, which, to some extents, represents the level of technological development in steel industry. Thickness feed-forward control in tandem cold mill plays an important roll in ensuring the thickness precision of cold rolled strip finished products. The thickness deviation of supplied materials is one of the significant causes for the thickness deviation of cold rolled strip finished products; therefore, the traditional thickness feed-forward control in a tandem cold mill is performed by the thickness deviations of supplied materials measured directly before frames.
The complexity of hot rolling process may thus result in performance fluctuation of the supplied materials, that is, the hot rolled products. The fluctuation thereof exhibits some degree of regularity. When a section of strip with said performance fluctuation enters each frame of the tandem cold mill, new thickness deviations may occur. Thus, it is of great significance for improving the thickness precision control to do research on the thickness feed-forward control method in the case of performance fluctuation of strips.
In the current thickness feed-forward control in a tandem cold mill, the thickness deviations of supplied materials measured directly before the frames S1, S2 and S5 are used for the feed-forward control. The adjustment mechanisms used for feed-forward control are hydraulic control systems of the frames S1, S2 and S5, respectively, and the principle thereof is shown as FIG. 1. Feed-forward control is mainly used for eliminating the instantaneous deviation, that is, when a large variation of the supplied material at the entry of a frame takes place, the hydraulic control systems of the frame takes actions correspondingly, so as to substantially eliminate the thickness deviations before exiting the frame.
Due to the higher requirements from users on the thickness precision of the cold rolled products as well as the complexity of hot rolling, it is necessary to take the effects of the performance fluctuation of the supplied material on the thickness deviations of finished products into consideration. The direct measurement on the performance of supplied materials before the tandem cold mill needs to add measuring instruments. However, the current measuring instruments have low precision. Additionally, this method needs to increase the equipment cost and corresponding maintenance personnel during manufacturing.